After this change, FrameProcessorChain chains any GlTextureProcessors
instead of only SingleFrameGlTextureProcessors.
The GlTextureProcessors are chained in a bidirectional manner using
ChainingGlTextureProcessorListener to feed input and output related
events forward and release events backwards.
PiperOrigin-RevId: 456478414
(cherry picked from commit 3a966916)
